GHC.IO.BufferedIO

Copyright	(c) The University of Glasgow 2008
License	see libraries/base/LICENSE
Maintainer	[email protected]
Stability	internal
Portability	non-portable (GHC Extensions)
Safe Haskell	Trustworthy
Language	Haskell2010

Description

Class of buffered IO devices

class BufferedIO dev where Source

The purpose of BufferedIO is to provide a common interface for I/O devices that can read and write data through a buffer. Devices that implement BufferedIO include ordinary files, memory-mapped files, and bytestrings. The underlying device implementing a Handle must provide BufferedIO.

Minimal complete definition

newBuffer, fillReadBuffer, fillReadBuffer0, flushWriteBuffer, flushWriteBuffer0

Methods

newBuffer :: dev -> BufferState -> IO (Buffer Word8) Source

allocate a new buffer. The size of the buffer is at the discretion of the device; e.g. for a memory-mapped file the buffer will probably cover the entire file.

fillReadBuffer :: dev -> Buffer Word8 -> IO (Int, Buffer Word8) Source

reads bytes into the buffer, blocking if there are no bytes available. Returns the number of bytes read (zero indicates end-of-file), and the new buffer.

fillReadBuffer0 :: dev -> Buffer Word8 -> IO (Maybe Int, Buffer Word8) Source

reads bytes into the buffer without blocking. Returns the number of bytes read (Nothing indicates end-of-file), and the new buffer.

emptyWriteBuffer :: dev -> Buffer Word8 -> IO (Buffer Word8) Source

Prepares an empty write buffer. This lets the device decide how to set up a write buffer: the buffer may need to point to a specific location in memory, for example. This is typically used by the client when switching from reading to writing on a buffered read/write device.

There is no corresponding operation for read buffers, because before reading the client will always call fillReadBuffer.

flushWriteBuffer :: dev -> Buffer Word8 -> IO (Buffer Word8) Source

Flush all the data from the supplied write buffer out to the device. The returned buffer should be empty, and ready for writing.

flushWriteBuffer0 :: dev -> Buffer Word8 -> IO (Int, Buffer Word8) Source

Flush data from the supplied write buffer out to the device without blocking. Returns the number of bytes written and the remaining buffer.